Android谷歌地圖在兩點之間繪製一條路徑

Question

我想繪製兩點之間的路徑並計算從A點移動到B點需要多少時間。我認爲這對於Google Maps API來說是微不足道的任務。

我發現的一切都是關於PolyUtil的小片段，其中documentation並沒有說明如何使用它。

我做了什麼？

裏面onMapReady方法我試圖創建一個編碼的路徑MapsActivity：

List<LatLng> latLngList = new ArrayList<>(); 
latLngList.add(new LatLng(56.952503, 24.083719)); 
latLngList.add(new LatLng(55.877526, 26.533898)); 

String encodedPath = PolyUtil.encode(latLngList); 

但是，什麼是下一個？如何在地圖上繪製此路徑？如何計算這些點之間的車/步行距離？

Answer 1

路徑是點的序列。其中一個解決方案是向谷歌地圖API發出HTTP請求，指定您的兩個位置作爲參數，並取回描述在兩點之間建立路徑所需的點的JSON。需要的代碼做如下：

1. 獲取路線URL需要調用谷歌地圖API

private String getMapsApiDirectionsUrl(LatLng origin,LatLng dest) { 
    // Origin of route 
String str_origin = "origin="+origin.latitude+","+origin.longitude; 

// Destination of route 
String str_dest = "destination="+dest.latitude+","+dest.longitude;   


// Sensor enabled 
String sensor = "sensor=false";    

// Building the parameters to the web service 
String parameters = str_origin+"&"+str_dest+"&"+sensor; 

// Output format 
String output = "json"; 

// Building the url to the web service 
String url = "https://maps.googleapis.com/maps/api/directions/"+output+"?"+parameters; 


return url; 

} 

執行URL在後臺致電

private class ReadTask extends AsyncTask<String, Void , String> { 

@Override 
protected String doInBackground(String... url) { 
    // TODO Auto-generated method stub 
    String data = ""; 
    try { 
     MapHttpConnection http = new MapHttpConnection(); 
     data = http.readUr(url[0]); 


    } catch (Exception e) { 
     // TODO: handle exception 
     Log.d("Background Task", e.toString()); 
    } 
    return data; 
} 

@Override 
protected void onPostExecute(String result) { 
    super.onPostExecute(result); 
    new ParserTask().execute(result); 
} 

} 

public class MapHttpConnection { 
    public String readUr(String mapsApiDirectionsUrl) throws IOException{ 
     String data = ""; 
     InputStream istream = null; 
     HttpURLConnection urlConnection = null; 
     try { 
      URL url = new URL(mapsApiDirectionsUrl); 
      urlConnection = (HttpURLConnection) url.openConnection(); 
      urlConnection.connect(); 
      istream = urlConnection.getInputStream(); 
      BufferedReader br = new BufferedReader(new InputStreamReader(istream)); 
      StringBuffer sb = new StringBuffer(); 
      String line =""; 
      while ((line = br.readLine()) != null) { 
       sb.append(line); 
      } 
      data = sb.toString(); 
      br.close(); 


     } 
     catch (Exception e) { 
      Log.d("Exception while reading url", e.toString()); 
     } finally { 
      istream.close(); 
      urlConnection.disconnect(); 
     } 
     return data; 

    } 
} 

創建解析器類從JSON解析數據列出pointes的

public class PathJSONParser { 

public List<List<HashMap<String, String>>> parse(JSONObject jObject) { 
    List<List<HashMap<String, String>>> routes = new ArrayList<List<HashMap<String,String>>>(); 
    JSONArray jRoutes = null; 
    JSONArray jLegs = null; 
    JSONArray jSteps = null; 
    try { 
     jRoutes = jObject.getJSONArray("routes"); 
     for (int i=0 ; i < jRoutes.length() ; i ++) { 
      jLegs = ((JSONObject) jRoutes.get(i)).getJSONArray("legs"); 
      List<HashMap<String, String>> path = new ArrayList<HashMap<String,String>>(); 
      for(int j = 0 ; j < jLegs.length() ; j++) { 
       jSteps = ((JSONObject) jLegs.get(j)).getJSONArray("steps"); 
       for(int k = 0 ; k < jSteps.length() ; k ++) { 
        String polyline = ""; 
        polyline = (String) ((JSONObject) ((JSONObject) jSteps.get(k)).get("polyline")).get("points"); 
        List<LatLng> list = decodePoly(polyline); 
        for(int l = 0 ; l < list.size() ; l ++){ 
         HashMap<String, String> hm = new HashMap<String, String>(); 
         hm.put("lat", 
           Double.toString(((LatLng) list.get(l)).latitude)); 
         hm.put("lng", 
           Double.toString(((LatLng) list.get(l)).longitude)); 
         path.add(hm); 
        } 
       } 
       routes.add(path); 
      } 

     } 

    } catch (Exception e) { 
     e.printStackTrace(); 
    } 
    return routes; 

} 

private List<LatLng> decodePoly(String encoded) { 
    List<LatLng> poly = new ArrayList<LatLng>(); 
    int index = 0, len = encoded.length(); 
    int lat = 0, lng = 0; 

    while (index < len) { 
     int b, shift = 0, result = 0; 
     do { 
      b = encoded.charAt(index++) - 63; 
      result |= (b & 0x1f) << shift; 
      shift += 5; 
     } while (b >= 0x20); 
     int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1)); 
     lat += dlat; 

     shift = 0; 
     result = 0; 
     do { 
      b = encoded.charAt(index++) - 63; 
      result |= (b & 0x1f) << shift; 
      shift += 5; 
     } while (b >= 0x20); 
     int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1)); 
     lng += dlng; 

     LatLng p = new LatLng((((double) lat/1E5)), 
       (((double) lng/1E5))); 
     poly.add(p); 
    } 
    return poly; 
}} 

的使用另一線程執行解析擴大性能

private class ParserTask extends AsyncTask<String,Integer, List<List<HashMap<String , String >>>> { 
    @Override 
    protected List<List<HashMap<String, String>>> doInBackground(
      String... jsonData) { 
     // TODO Auto-generated method stub 
     JSONObject jObject; 
     List<List<HashMap<String, String>>> routes = null; 
     try { 
      jObject = new JSONObject(jsonData[0]); 
      PathJSONParser parser = new PathJSONParser(); 
      routes = parser.parse(jObject); 


     } catch (Exception e) { 
      e.printStackTrace(); 
     } 
     return routes; 
    } 

    @Override 
    protected void onPostExecute(List<List<HashMap<String, String>>> routes) { 
     ArrayList<LatLng> points = null; 
     PolylineOptions polyLineOptions = null; 

     // traversing through routes 
     for (int i = 0; i < routes.size(); i++) { 
      points = new ArrayList<LatLng>(); 
      polyLineOptions = new PolylineOptions(); 
      List<HashMap<String, String>> path = routes.get(i); 

      for (int j = 0; j < path.size(); j++) { 
       HashMap<String, String> point = path.get(j); 

       double lat = Double.parseDouble(point.get("lat")); 
       double lng = Double.parseDouble(point.get("lng")); 
       LatLng position = new LatLng(lat, lng); 

       points.add(position); 
      } 

      polyLineOptions.addAll(points); 
      polyLineOptions.width(4); 
      polyLineOptions.color(Color.BLUE); 
     } 

     googleMap.addPolyline(polyLineOptions); 

    }} 

當要得到兩個點的路徑

String url = getMapsApiDirectionsUrl(latlngOne, latlngTwo);      
    ReadTask downloadTask = new ReadTask();  
    // Start downloading json data from Google Directions API 
    downloadTask.execute(url); 

爲了計算點之間的距離

float[] results = new float[1]; 
Location.distanceBetween(latLongA.latitude, latLongB.longitude, 
         latLongB.latitude, latLongB.longitude, 
         results); 

結果將在m eters